Project Summary: Despite immense efforts in behavioral interventions to promote safe sexual practices, vaginal HIV transmission continues to be pandemic worldwide. An HIV-specific, safe, effective and discreet vaginal method that does not require daily or sex-associated dosing may provide a powerful prevention tool addressing the current gap in behavioral and pharmacological interventions. Human monoclonal antibodies (mAb) delivered locally to the vagina offer exceptional promise combining safety, efficacy and unparalleled specificity. Importantly, by delivering mAb to the vagina rather than systemically, far lower doses of mAb are needed to reduce the risks of vaginal HIV transmission, leading to orders of magnitude in cost savings. Adding further to the promise of vaginal applications of mAb, the Lai and Cone Labs recently discovered a novel IgG effector function in mucus ? IgGs that trap individual pathogens in mucus ? and have pioneered a technology enhancing the potency of mAb in mucosal secretions based on carefully-tuned affinity between IgG-Fc and mucins. We have shown that engineered mAb can consistently trap Herpes viruses in human cervicovaginal mucus (CVM) across the menstrual cycle and from women with diverse vaginal microbiota, with 10-fold greater potency than protection by neutralization. Trapping alone (with a non-neutralizing mAb) directly prevented vaginal Herpes transmission in mice. In pilot studies, we also found that anti-HIV mAb VRC01 can similarly trap HIV in CVM. Currently, the major hurdle to translating this vaginal immunoprophylaxis strategy for HIV is a method for sustained delivery of mAb at low doses. Vaginal microbicide trials have shown that methods that do not require daily or sex- associated dosing, such as intravaginal rings (IVR), are far more likely to maximize user compliance. Unfortunately, most current IVRs are designed to deliver small molecule drugs, and are ill-suited for delivering mAb, particularly at low release rates. To address this, Mucommune has been developing a unique capsule- containing IVR system that can provide sustained release of appropropriate doses of mAb for over 30 days, while protecting the encapsulated mAb from degradation in the vaginal environment. Our goal here is to design and formulate a capsule-IVR that can continuously release into human CVM 0.05-0.2 mg/day of two promising broadly neutralizing mAb against HIV (VRC01 and N6). In Aim 1, we will load mAb into capsules, measure release kinetics in vaginal simulant buffer, and characterize mAb integrity before/after loading and after release. In Aim 2, we will incubate mAb-loaded capsules in fresh human CVM, and measure the HIV neutralization and trapping potency of encapsulated and released mAb. Successful completion of these studies will lead to a Phase II proposal, with the goal of developing a shelf-stable capsule-IVR that slowly releases mAb against HIV, providing effective protection against vaginal HIV transmission with convenient once a month application. By enabling enhanced mAb function in mucus, we expect Mucommune will help pave the way for mAb-based potent protection against a broad array of pathogens at major mucosal surfaces.